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Panel of scientists also says with near certainty that humans are causing climate change

An international panel of scientists has warned that sea levels could rise 3 feet by 2100 if steps are not taken to curb emissions. The group has previously avoided issuing predictions about sea level changes. The scientists also concluded with near certainty that human activity is the source of most temperature increases over the past few decades.

The IPCC, which won the 2007 Nobel Peace Prize together with former Vice President Al Gore, consists of several hundred scientists. The group publishes summaries every five to six years and has significant influence among world leaders. Its findings have, in the past, led to hundreds of billions of dollars in spending to stem the tide of greenhouse gases around the world.

"It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010," the draft report says. "There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level and changed some climate extremes in the second half of the 20th century."

The latest report is the fifth such assessment by the IPCC, founded in 1988. With each passing report, the group concludes with increased certitude that humans are the primary force behind climate change.

The group stepped back a bit from its previous stance on global warming that results from carbon dioxide, saying global temperatures could rise by 2.7 degrees Fahrenheit -- a significant decrease from previous estimates that the rise would be about 3.6 degrees.

Still, the draft warns that such a low number is only a possibility, and the chances of warming being so low is unlikely. Current evidence points to an increase greater than 5 degrees Fahrenheit if carbon dioxide levels double.

That much of an increase would result in widespread melting of land ice, extreme heat waves, challenges in food growth and dramatic changes in plant and animal life, including a potential wave of extinctions.

The report, which still has to go through a final review and negotiation between scientists and world leaders in Stockholm next month, is not yet public. But based on previous reports, most of the core findings are likely to be included in the final version of the document.

The IPCC doesn't conduct its own research, but rather analyzes published scientific literature focused on climate change. The group became a political target for skeptics of climate change after winning the Nobel Peace Prize.

When skeptics found minor errors in the 2007 report, the group adopted a set of rigorous procedures to prevent a repeat of such mistakes. Some skeptics challenge the notion that the earth is warming at all; others who acknowledge that it is say humans are not to blame and that the risks are likely to be small and manageable.

All of the world's scientific bodies have warned that global warming is a serious problem that must be addressed.